And there is mounting concern over the spread of heroin, with the drug being involved in more deaths in 2008, compared to 2007.

But statistics show that legal substances, including tranquillisers and alcohol as well as anti-depressants and methadone, are involved in the bulk of drug deaths.

There were 524 drug-related deaths in 2008, some 293 of which were direct poisonings from one or more drugs.

Of the 293 deaths:

– Anti-depressants were involved in 77 deaths, up from 47 in 2007 (+64%).

– Methadone was implicated in 78 deaths, compared to 53 in 2007 (+32%).

– Heroin was involved in 86 deaths, compared to 78 in 2007 (+7%).

– Cocaine was linked to 58 deaths, down from 66 in 2007 (-12%).

The National Drug-Related Deaths Index, compiled by the Health Research Board, shows that prescribed tranquillisers, known as benzodiazepines, continue to be implicated in most deaths (117), although this was a reduction on 2007 (123).

Other prescription drugs were linked to 59 deaths, down from 62. Alcohol was involved in 70 deaths, a drop from 85.

The typical age of poisoning deaths was 35, including 13 deaths among 15-19 year olds and 30 aged 20-24.

Daithí Doolan, of CityWide Drugs Crisis Campaign, said the involvement of prescription drugs in so many deaths raised “serious questions” about prescription practices.

Speaking at the launch of their election campaign, he said if these issues were not a priority for the next government “unfortunately there will be more and more people buried”.

The index shows the number of poisonings rose in Dublin. Outside Dublin, the south-east accounted for the most deaths (34, up from 28 in 2007).

Paul Delaney, of the Cornmarket Project in Wexford, described the south-east figure as “shocking” and said there continued to be a “dearth of treatment services” in the area.

The report said there were a total of 524 deaths in 2008, compared to 535 in 2007 (the highest ever), but said the 2008 figure is “likely to be revised upwards”.

The remaining deaths in 2008 — 231 — were due to non-poisonings: 120 from medical causes, such as drug-related infections, and 101 from trauma, such as suicides or risky behaviour.

Meanwhile, separate figures show the number of people to have officially died by suicide in Cork has risen by more than 50% since the start of the economic crisis.

Latest figures detailed at the HSE South regional health forum show that in 2008 a total of 64 people lost their lives in this way. By the end of 2009 this surged to 93.